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monocotman

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Leslie,
many thanks for this. I think you’ve covered everything. I will definitely have a rethink of my growing areas.
David
 

Ray

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I think that’s more likely a pathogen than a cultural issue, but we do have to keep in mind that poor culture (thinking about the possibility of changes in the media) can make plants more susceptible to pathogens.

I doubt it’s a calcium issue, as a deficiency typically affects newly-growing tissues, not existing, already-grown stuff.

If the potting medium question has been eliminated, I’d start by treating with a copper-based systemic.
 

SouthPark

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repotting them at the correct time, when new roots are appearing from the new shoot.
MM ----- I reckon the general rule-of-thumb that people pass around ---- about repotting when new roots are appearing .... is just a rule-of-thumb. I repot any catt and pretty much any of my tropical orchids at any time, and nothing bad will happen to them. Some people mention bifoliate catts - in particular bifoliate species catts - really need to be repotted when roots are sprouting etc. I don't think that's correct either. I'll repot any regular sort of catt --- species or hybrid - bifoliate or unifoliate. Any time.

The rule-of-thumb probably doesn't strictly equate to 'the correct time' for repotting. I believe it just depends on how the orchid is grown and cared for there-after (- after a potting/repotting that is).

My remarks definitely don't mean to tell people that they themselves can repot at any time. The rule-of-thumb probably helps some or many growers (avoid orchid issues) in one way or another.
 
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alex.sorensen51

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I agree,with the problem being cultural. The pre-amble is ,I was one of the first to create a database of cultural care for a 2000 plant collection,way back when computers used dot matrix printers and rolls of paper.What I found was ,when orchids don't get re-potted on time,they develop all kinds of contagion based on media breaking down,and not allowing air around the "roots", thus creating the perfect storm for virus',fungi,and mineral build-up. In your situation,I had a very similar problem,and it turned out to be fusarium wilt,with the characteristic purple veination in the stem and lower basal area,and "root" die-off.If you have species plants...immediately de-pot,sterilize,and repot using lots of styrofoam with bark.You may be able to have it grow out of the problem,if you use much more frequent re-potting cycles.
 

SouthPark

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This is also where the idea of occasional media dry-out ------ how occasional .... not sure, but just sometimes ........ could possibly help to deal with certain unwanted activity (growth or build-up of things) inside the pot and in the media and on roots etc. This is aside from the other benefit of sometimes giving the roots a little bit of a breather from a dry out.

It is true that some orchids adapted to some conditons are exceptions. So there will always be exceptions to cases. But totally agree ------ if we purposely do things to make things hard for certain unwanted organisms from doing their unwanted activities, then that is a good thing.
 

monocotman

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So here is where we are now. I’ve just ordered 80 litres of orchiata from my regular supplier. The plan from now on is to repot strictly on a 2 year basis.
In fairness since Covid hit I have been repotting many of the catts at the appropriate time. I have got through a 40 litre bag of orchiata this summer which is about a third of the collection.
The communal collection trays will have to stay, they are too convenient plus they shade the mostly black pots from the direct sun but what I can do is to take the pots out of them to water. As there is LECA in the bottom To keep the pots off the floor, there should then be no cross contamination of pots with water.
The issue of moving air is more problematic. I take your point Lesley about fans, but in a domestic setting, they are very awkward. I am careful with the south facing windows especially, to open the top small windows when there is any chance of heat stress and sunburn. This stops all but the very occasional problem with scorch.
The leaves are never wet so there is very little chance of problems here, the only issues I have with the leaves is scale, with which I have a running battle. I am now on top of it but you need to be eternally vigilant and it means I need to inspect all plants every couple of weeks at least, which isn’t a bad thing.
I am interested in your comments about watering and it being ok in your conditions for the plants to sit in a bit of water as long as it dries out with a couple of days. I have noticed that a couple of my catts that were wettter than normal grew bigger pseudobulbs and this suggest that maybe I am under watering some of mine, but it’s a fine line to tread when I am not keeping an airflow over them and they could sit wet for too long and clause all the issues we have been speaking of.
I am going to try this next year in summer by keeping the plants that are in active growth slightly wetter than the others, by reducing the time between watering.
Anyway, a huge thank you to everyone who has contributed to this thread, especially Dr Leslie, I have now got to go and put what I’ve learned into practise!
Yay slippertalk!
A4E8B1B8-0964-405A-AAD7-C46D8D887643.jpeg
the photo shows the traysin the south facing windows with the silver foil covering the radiators to deflect the heat away from the leaves.
 
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Ray

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Let’s think about this repotting “rule of thumb”.

As roots grow, the root structure - cell types, shape, size, and number, from the cortex through velamen - is tailored to the environment in which the grow, and once grown, cannot change.

That said, just as new roots are emerging is, without a doubt, the best time to repot, so those new roots will grow to be optimal for the environment.

I think that the factor that makes people differ in their opinion of that being essential versus a general recommendation depends upon potential changes in the root environment. For example, if - using the example above - you use a relatively stable medium and replace it regularly, before it decomposes to a significant degree, the “old” and “new” environments are pretty similar, so the root function is relatively unaffected. In that case, waiting for new roots to emerge isn’t a big deal.

Now jump to someone changing potting media or culture - bark to semi-hydroponics, for example - and there will be a drastic difference between the old and new conditions, so the emergence of new roots is almost essential, as the old ones will not function well in the new environment, putting the plant at risk as the sub-optimal roots fail.

The rate of root failure and necessity of new root emergence is mostly determined by the degree of difference. Between the old and new conditions. I recently move all my phals from sphagnum to rock wool cubes - a walk in the park. If I was moving a cattleya from coarse Orchiata into them, I’d pat far more attention to the timing.

Now then, this doesn’t even take into account the differences between plants or cultural conditions. A plant grown with summer sun, warmth and humidity is likely to carry on more easily that one in winter, cool and more arid conditions.
 

DrLeslieEe

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I switched my cattleyas to semi-water culture (SWC) because they were not rooting into the media and were gettting more dehydrated. I was pretty much desperate as the bulbs were shrinking too much, almost desiccated. Then I saw my orchid buddy grow his catt hybrids in SWC and they were thriving. I thought why not try mine in them. And it worked... for my dry indoor conditions of 35-45% humidity.

The results became evident in a few months. I switched over in fall last year as first experiment and then most in spring and late summer this year.

I saw roots grow into the mix and the bulbs were more plump than usual. The important thing is to let the root dry for a day or two. This method allows the roots to soak in more water over a longer time. As my buddy says ‘they’re thirsty’!

I’m attaching a few pics to show this:

21A3C142-8EEA-4095-9C5C-1FE76F804C28.jpegF4398442-D25D-428C-9387-6171AC2D7769.jpeg97F7744F-184E-4C14-A521-905D47418E39.jpeg

Above, you can see the root grow into the media. And the bulbs plump and leaves not desiccated. These are all species.

The pic below shows what happens if a deep water reservoir is not detected by roots from SWC, and roots everywhere except inside bark.

F3F68A53-A2EA-4CB3-B881-90EE2D4A62EF.jpeg

As you can see, it’s a mess of roots that attached everywhere.

The layers in this SWC pot is bottom inch of clay pebbles (LECA) or large perlite, middle 2-3 inch of orchiata/perlite/charcoal (ration 3:2:1), and top inch layer of NZ moss.

As for air, I attach mini fans on top of the plants on the shelf to keep air movements 24-7. They blow the light heat away from top of leaves as well as introduce fresh cooler air from window and room. See pic below of one of my cattleya shelves.

81DC9E90-21BA-4ACE-A6D6-44C3A25E904E.jpeg

All the cattleyas have their own plastic trays to trap water. Roots grow in search of this water, so they stay in there! Makes a cleaner looking plant.

Caveat: this method works for me. Might not for everyone, so watch carefully not to rot roots.
 

DrLeslieEe

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Hehe I was wondering if anyone would notice.

I decided on those smiling shades to keep my cattleyas think happy thoughts lol
 

Ozpaph

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I wonder if the deep plastic trays diminish airflow around the pot and root area, facilitating rot. I would try a shallower vessel. Catts grow on trees with lots of air around the roots. An idea to contemplate.
 

SouthPark

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I wonder if the deep plastic trays diminish airflow around the pot and root area, facilitating rot. I would try a shallower vessel. Catts grow on trees with lots of air around the roots. An idea to contemplate.
It is true OP. Very true. It probably also depends on whether the roots of a catt are adapted to lower oxygen level environments or wet environments (or not). But in general ----- for regular catt roots, I like the suggestions about air-flow around the roots ----- through the media etc. A shallow pot and airy media will definitely help in that way.

One method I use that works for wide pots (or wide-enough) pots - that can also be deep too ---- is the method of dumping most of the water toward the outskirts of a suitably large size pot. If the bulk of media in the pot (such as the central region - and down in the deep dark depths) is prevented from becoming a wet slush/slurry/sludgy saturated mix --- especially around the bulk of the roots ----- then that will help catts (and other orchids) out ----- by not getting into long-time wet roots condition.

When watering the outskirts of the pot, while having the inner regions dryer (much less wet) ..... it might be possible that (using a pot having good size drainage holes at the bottom) the roots can have nice humid conditions to grow well ----- with a wet/dry gradient inside the pot.

If an orchid grower finds that - when they unpot a catt and see a big mass of soft mushy gray/olive/dark water logged roots ...... then the pot may just not be large/wide enough, or the media not quite airy enough, or the watering strategy/plan isn't suitable. Also knowing that 'very cold plus very wet' isn't good too for roots.

There can be exceptions. For example ----- if an orchid just-so happens to have its roots grow out (naturally reach out) into a very wet medium, then its roots may well somehow 'adapt' to that particular wet or low oxygen environment. So some people expecting to pull out a mass of mushy dead roots can sometimes be 'surprised' when they see a mass of nice green/white wet roots. It can mean the roots 'adapted' to the environment. But roots apparently (we've been told) can handle low-oxygen watery environments up to a point or a limit. So that just means growers be 'warned' about what could happen ..... such as a mass of nice adapted green/white roots could take a dive in health if something doesn't go well - such as bacterial activity/rotting starts up if portions of roots get into trouble due to not enough O2 ----- then one thing leads to another.

So - keeping control of the conditions within the pot and in/around the roots is very important (this is well-known) ---- aside from the conditions in and around the leaves/stem (temperature and temperature changes and rates of temperature changes, air-movement etc).
 
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southernbelle

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It is true OP. Very true. It probably also depends on whether the roots of a catt are adapted to lower oxygen level environments or wet environments (or not). But in general ----- for regular catt roots, I like the suggestions about air-flow around the roots ----- through the media etc. A shallow pot and airy media will definitely help in that way.

One method I use that works for wide pots (or wide-enough) pots - that can also be deep too ---- is the method of dumping most of the water toward the outskirts of a suitably large size pot. If the bulk of media in the pot (such as the central region - and down in the deep dark depths) is prevented from becoming a wet slush/slurry/sludgy saturated mix --- especially around the bulk of the roots ----- then that will help catts (and other orchids) out ----- by not getting into long-time wet roots condition.

When watering the outskirts of the pot, while having the inner regions dryer (much less wet) ..... it might be possible that (using a pot having good size drainage holes at the bottom) the roots can have nice humid conditions to grow well ----- with a wet/dry gradient inside the pot.

If an orchid grower finds that - when they unpot a catt and see a big mass of soft mushy gray/olive/dark water logged roots ...... then the pot may just not be large/wide enough, or the media not quite airy enough, or the watering strategy/plan isn't suitable. Also knowing that 'very cold plus very wet' isn't good too for roots.

There can be exceptions. For example ----- if an orchid just-so happens to have its roots grow out (naturally reach out) into a very wet medium, then its roots may well somehow 'adapt' to that particular wet or low oxygen environment. So some people expecting to pull out a mass of mushy dead roots can sometimes be 'surprised' when they see a mass of nice green/white wet roots. It can mean the roots 'adapted' to the environment. But roots apparently (we've been told) can handle low-oxygen watery environments up to a point or a limit. So that just means growers be 'warned' about what could happen ..... such as a mass of nice adapted green/white roots could take a dive in health if something doesn't go well - such as bacterial activity/rotting starts up if portions of roots get into trouble due to not enough O2 ----- then one thing leads to another.

So - keeping control of the conditions within the pot and in/around the roots is very important (this is well-known) ---- aside from the conditions in and around the leaves/stem (temperature and temperature changes and rates of temperature changes, air-movement etc).
One thing I do in deep 7” or all 8” - 10” (my largest) pot, is to put a 2” net pot upside down in the center bottom (secured with twist ties) and use a soldering iron to put holes in the center bottom of the pot under the net pot for air to enter. Keith Davis recommended the net pot idea.
I also use either power+/super mix or all super (both with perlite/charcoal) in 7” or above. Very airy mix and airy center. I still go 7-10 days in summer and 10-12 in winter between watering in biggest pots, with fans and temp/humidity control. But roots usually look good on repot.
 

SouthPark

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SB - thanks for sharing and explaining the method that you use. I have heard of that very useful method. That one will definitely help cut down on water logging issues.
 

monocotman

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This an update in the improvements I’ve been able to make following the recommendations of Dr Leslie and others.

Firstly all the affected plants have either been isolated or thrown away. I lost the labiata alba ‘angerer’ soon after I had posted it to rot. Most annoying.

Next all plants that were not repotted earlier this year have been repotted.

Then any plants that were growing anywhere close to rotted ones have been given the ‘bleach’ treatment. This involves soaking the plants for 10mins in a bucket of water to which has been added 1 tablespoon of household bleach, pot and all the foliage. They are then given 10 mins in a bucket of water without bleach. This is pretty good at killing most things, bugs included and maybe any surviving rot spores.
Lastly they have all be put into their own planters to stop cross contamination when watering.
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this is the purpurata room. All growing well.
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this is the sitting room where the rot happened. Fingers crossed.
David
 

abax

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David, I was going to suggest that you switch to slotted clay pots with the Orchiata,
charcoal and perlite, however, since you've already repotted...too late. I do wish
you consider clay pots with holes or slots for your Catts.
 
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